Aug 12, 2009
Omegatron re-cycled some Wiki charts and we are happy to report that they are great improvements over the originals. I welcome other readers to alert us when you have done your bit of community outreach, by ridding the world of chartjunk. The email address is the name of the blog at gmail for any submissions.
Not surprisingly, the originals were pie charts.
Why are pie charts such poor tools for communications? Think about where we can place the message, and you'll find that this chart type is far too rigid. In a pie chart, the key resource is the relative size of the sectors, followed by the number of sectors, and sometimes the size of the total pie. Other than those, there are little else useful in a pie chart.
The histograms used by Omegatron are much more flexible. There can be information encoded in the height of the bars, the width of the bars, the total area, the relative distribution of bar areas, the existence and location of peaks and troughs, etc. etc.
For comparing data collected in slightly different formats, the pie charts are hopeless. Notice that the lowest category on the left (pink) corresponds to 8 weeks or less, which would include two and a half sectors on the right plus potentially a missing sector for 4 weeks or less. The histograms below handle this easily.
Omegatron asked for some feedback. I think the new ones are significantly better. A few minor points:
- Instead of coloring the background to the chart, I'd color the bars themselves into green/yellow/orange according to the trimester
- I'd put the trimester labels under the horizontal axis, close to the "week" labels
- The charts obviously need to identify the country and year of the data (which I added). Omegatron pointed me to an inexplicable Wiki convention of not putting text inside charts (see here). I must disagree with this convention. Annotations on charts are some of the most useful things.
- If these two charts are to be placed side by side for comparison, then we need to sort out the vertical scale. It cannot be the absolute number of abortions but some kind of relative scale in proportion to the population size, or some similar metric.
- In addition, if comparison is the point, I'd suggest an overlapping histogram with bars having no fill.
Great work! And I love to see more of it!
The fact of not putting text in an image also makes sense in a multi-lingual context such as wikipedia. You would end-up with great images integrating Chinese characters on an English page.
Posted by: CKL | Aug 13, 2009 at 09:30 AM
Yes, that's the rationale behind the rule. It's relatively difficult to photoshop a raster image of a chart with text in it and replace the text with another language without screwing up what's behind the text, so they prefer leaving the description in the caption in the article, which can be edited and translated by anyone.
With SVG charts this is not as much of an issue, since you can just edit the source code and change the text directly, but it still requires uploading a separate SVG for each language, rather than just re-using the same image on all language wikis without modification.
Posted by: Omegatron | Aug 14, 2009 at 11:39 AM